1. Field of the Invention
The present invention relates to heterocyclic compounds, which are imidazolone derivatives having human neutrophil elastase inhibitory properties, and their use in therapy.
2. Discussion of the Background
Human neutrophil elastase (HNE) is a 32 kDa serine proteinase found in the azurophilic granules of neutrophils. It has a role in the degradation of a wide range of extracellular matrix proteins, including fibronectin, laminin, proteoglycans, Type III and Type IV collagens as well as elastin (see Bieth, G. In Regulation of Matrix accumulation, Mecham, R. P. (Eds), Academic Press, NY, USA 1986, 217-306, which is incorporated herein by reference in its entirety). HNE has been for long considered to play an important role in homeostasis through repair and disposal of damaged tissues via degradation of the tissue structural proteins. It is also relevant in the defense against bacterial invasion by means of degradation of the bacterial body. In addition to its effects on matrix tissues, HNE has been implicated in the upregulation of IL-8 gene expression and also induces IL-8 release from the epithelial cells of the lung. In animal models of Chronic Obstructive Pulmonary Disease (COPD) induced by tobacco smoke exposure both small molecule inhibitors and protein inhibitors of HNE inhibit the inflammatory response and the development of emphysema (see Wright, J. L. et al. Am. J. Respir. Crit. Care Med. 2002, 166, 954-960; and Churg, A. et al. Am. J. Respir. Grit. Care Med. 2003, 168, 199-207, both of which are incorporated herein by reference in their entireties). Thus, HNE may play a role both in matrix destruction and in amplifying inflammatory responses in chronic respiratory diseases where neutrophil influx is a characteristic feature. Indeed, HNE is believed to play a role in several pulmonary diseases, including COPD, cystic fibrosis (CF), acute respiratory distress syndrome (ARDS), pulmonary emphysema, pneumonia and lung fibrosis. It is also implicated in several cardiovascular diseases in which tissue remodelling is involved, for example, in heart failure and the generation of ischaemic tissue injury following acute myocardial infarction.
COPD is an umbrella term encompassing three different pathological conditions, all of which contribute to limitation of airflow: chronic bronchitis, emphysema, and small-airway disease. Generally all three will exist to varying extents in patients presenting with COPD, and all three may be due to neutrophil-mediated inflammation, as supported by the increased number of neutrophils observed in bronchoalveolar leakage (BAL) fluids of COPD patients (see Thompson, A. B.; Daughton, D.; et al. Am. Rev. Respir. Dis. 1989, 140, 1527-1537, which is incorporated herein by reference in its entirety). The major pathogenic determinant in COPD has long been considered to be the protease-anti-protease balance (also known as the “elastase:anti-elastase hypothesis”), in which an imbalance of HNE and endogenous antiproteases such as al-antitrypsin (α1-AT), secretory leukocyte protease inhibitor (SLPI) and pre-elafin leads to the various inflammatory disorders of COPD. Individuals that have a genetic deficiency of the protease inhibitor α1-antitrypsin develop emphysema that increases in severity over time (see Laurrell, C. B.; Erikkson, S Scand. J. Clin. Invest. 1963 15, 132-140, which is incorporated herein by reference in its entirety). An excess of HNE is therefore destructive, leading to the breakdown of pulmonary morphology with loss of elasticity and destruction of alveolar attachments of airways in the lung (emphysema) whilst simultaneously increasing microvascular permeability and mucus hypersecretion (chronic bronchitis).
Several human neutrophil inhibitors have been disclosed so far in the art. In particular, International Patent Applications WO2011/110858, WO2011/110859, and WO 2014/009425, all of which are incorporated herein by reference in their entireties, describe some pyrimidine derivatives having human neutrophil elastase inhibitory properties and their use in therapy.
Although several HNE inhibitors have been disclosed so far as above reported, there is still a need for further HNE inhibitors. Particularly, there is still a need for further HNE inhibitors endowed with a high potency for HNE enzyme inhibition. Particularly advantageous would also be the identification of further HNE inhibitors endowed with a high potency for HNE enzyme inhibition and which would show an appropriate developability profile as an inhalation treatment or oral treatment.